A PMR write head has a main pole with a small surface area at an air bearing surface (ABS), and coils that conduct a current and generate magnetic flux in the main pole such that the magnetic flux exits through a write pole tip and enters a magnetic medium (disk) adjacent to the ABS during a write process. Magnetic flux is used to write a selected number of bits in the magnetic medium and typically returns to the main pole through a trailing loop pathway. The trailing loop comprises a trailing shield structure with a PP3 shield portion that arches over the write coils and connects to a top surface of the main pole layer through a back gap magnetic connection (BGC). The trailing shield structure at the ABS typically has a high Ms (19-24 kG) layer called a hot seed layer that adjoins a top surface of the write gap. A good hot seed response is required to reduce stray fields in the side shields, and in a leading shield when present. Above the hot seed layer at the ABS is a second trailing shield layer with a lower Ms (16-19 kG) to control ATE. Generally, the second trailing shield and BGC are deposited (plated) at the same time. Subsequently, the PP3 trailing shield is deposited on the second trialing shield and BGC, and has a front side that is recessed from the ABS.
A PMR head which combines the features of a single pole writer and a double layered medium (magnetic disk) has a great advantage over longitudinal magnetic recording (LMR) in providing higher write field, better read back signal, and potentially much higher areal density. In addition to conventional magnetic recording (CMR), shingled magnetic recording (SMR) is another form of PMR and has been proposed for future high density magnetic recording by R. Wood et al. in “The Feasibility of Magnetic Recording at 10 Terabits Per Square Inch on Conventional Media”, IEEE Trans. Magn., Vol. 45, pp. 917-923 (2009). Track widths are defined by the squeeze position or amount of overwrite on the next track rather than by write pole width as in today's hard disk drives. One of the main advantages of shingled writing is that write pole width no longer needs to scale with the written track width. Thus, the opportunity for improved writability and higher device yield is not restricted by pole width as a critical dimension to be tightly controlled. Secondly, adjacent track erasure (ATE) becomes less of an issue because tracks are written sequentially in a cross-track dimension and only experience a one-time squeeze from the next track.
For both conventional magnetic recording (CMR) and shingle magnetic recording (SMR), continuous improvement in storage area density is required for a PMR writer. A write head that can deliver or pack higher bits per inch (BPI) and higher tracks per inch (TPI) is essential to the area density improvement. Improved TPI is generally realized through better side shield designs while BPI on-track performance is promoted primarily through high Ms material in the trailing shield.
It is desirable to modify the trailing shield layout in order to improve writer speed and enhance BPI for advanced writer technology. However, coil thickness, coil spacing, and trailing shield thickness are parameters that limit adjustments to the current trailing shield structure. Improved designs have heretofore been prevented by significantly higher process complexity and higher cost necessary to implement significant changes in the aforementioned parameters. Therefore, an improved trailing shield design is needed that can deliver higher writer speed and BPI to meet the requirements for advanced PMR writers, and that can be fabricated with a process and cost acceptable to large scale manufacturing.